1. Field of the Invention
The present invention relates to an apparatus and method for driving a plasma display panel (PDP), and more particularly, to an apparatus for recovering energy using a magnetic coupled inductor for driving a PDP and a method for designing the same so that reactive power and heat dissipation amount are reduced without having an additional isolation gate driver. The present application is based on Korean Application No. 2001-52110, filed Aug. 28, 2001, which is incorporated herein by reference.
2. Description of the Related Art
A conventional PDP is a next generation flat display device for displaying characters and images by using plasma which is generated by gas discharge. Depending on the size of the PDP, several hundred thousand to several million pixels are arranged in the PDP in the form of a matrix.
FIG. 1 shows the structure of a conventional alternating current-PDP (AC-PDP) sustain discharge circuit, which is suggested by U.S. Pat. No. 4,866,349 to Weber et al. In the case of the AC-PDP, a display panel is assumed as a load having a panel capacitance Cp. The basic operation of a PDP driving circuit is described in Weber et al.
FIGS. 2a through 2j show an output voltage Vp according to a switching sequence and the waveforms of current IL, which flows through an inductor Lc. The AC-PDP sustain discharge circuit is represented as the following four modes according to the switching sequence.
(1) Mode 1
Before a metal oxide semiconductor field effect transistor (MOSFET) switch Sa1 becomes conductive, a MOSFET switch Sx2 is conductive and an output voltage Vp between both terminals of a panel is maintained as 0V. When the MOSFET switch Sa1 becomes conductive at time t0, mode 1 operation starts. An LC resonance circuit is formed through a path of Cc1-Sa1-Da1-Lc1-Cp (panel) so that a resonance current flows through an inductor Lc1 and the output voltage Vp increases. The current of the inductor Lc1 becomes 0 and the output voltage Vp becomes a voltage +Vpk at time t1.
(2) Mode 2
The MOSFET switch Sa1 is opened and a MOSFET switch Sy1 is closed at time t1. Here, the voltage between the drain and source of the MOSFET switch Sy1 has a sudden change as a voltage Vpk at time t1 so that a switching loss is caused. In mode 2, the output voltage Vp is maintained as a voltage +Vs and the panel maintains discharge.
(3) Mode 3
A MOSFET switch Sa2 is closed and the MOSFET switch Sy1 is opened at time t2. The LC resonance circuit is formed through a path of Cp (panel)-Lc1-Da2-Sa2-Cc1 in mode 3 so that the resonance current flows through the inductor Lc1 and the output voltage Vp is reduced. The current of the inductor Lc1 becomes 0, and the output voltage Vp becomes a voltage +Vpk at time t3.
(4) Mode 4
The MOSFET switch Sa2 is closed and a MOSFET switch Sy2 is opened at time t3. Here, the voltage between drain and source of the MOSFET switch Sy2 becomes xe2x88x92Vpk at time t3 so as to generate a switching loss. The output voltage Vp is maintained as 0V in mode 4. If the MOSFET switch Sx2 is closed and the MOSFET switch Sb1 is opened at time t0xe2x80x2, another half period is repeated.
The conventional energy recovering circuit requires four switches so that the number of gate drivers is increased, and further requires an isolation gate driver since the switches in the energy recovering unit are not grounded. As a result, an ideal switching operation is difficult to achieve when high frequency switching is performed. In case that switching-on time is very short (300 ns), the switching-on operation cannot be performed during the delay time of the isolation gate driver, resulting in improper operation. Additionally, in case that a panel resistive device and a device resistance exist, a sudden change occurs in the panel voltage as shown in FIG. 2i. As a result, an electromagnetic interference (EMI) and a reactive power increase.
To solve the above-described problems, it is an objective of the present invention to provide an apparatus for recovering energy using a magnetic coupled inductor and a method for designing the same so as to reduce the number of energy recovering circuit elements by using a magnetic coupled inductor circuit and to reduce reactive power and electromagnetic interference (EMI).
To accomplish the above-described object, according to the present invention there is provided an apparatus for recovering energy using a magnetic coupled inductor in a plasma display panel (PDP) driving system, the apparatus comprising: first and second switching means for switching on and off an electric connection between an input terminal and the ground in correspondence to a predetermined energy recovering sequence switching control signal; and a magnetic coupled inductor in which first and second coils are magnetically coupled by respectively connecting first terminals of the first and second coils to both terminals of a PDP and by respectively connecting second terminals of the first and second coils to input terminals of the first and second switching means.
A method for designing an energy recovering circuit using a magnetic coupled inductor in a PDP driving system according to the present invention to accomplish another objective comprises the steps of: performing a switching process in which the magnetic coupled inductor whose first and second coils are magnetically coupled is connected to both terminals of a PDP; and currents of the first and second coils are connected to or disconnected from the ground in correspondence to a predetermined energy recovering sequence, so that the voltage of the PDP is linearly charged/discharged at a charge/discharge mode in a sustain section.